In order to receive bits of digitally transmitted data, synchronization with the respective data bits is required. Reproduction of synchronizing clock signals from information contained in the transmitted data is employed. The arrangement of an example of reproducing circuits is as follows. Received data is differentiated in a differentiation circuit to produce transition pulses responsive to rising of the received data. The transition pulses are inputted to a LC resonant circuit, which generates a resonant signal. The values of a coil and a capacitor forming the resonant circuit are adjusted in such a manner as to provide the resonant signal with given resonant frequency and phase synchronized with the frequency of the transmission rate of the received data. The resonant signal is applied to a comparator, where it is shaped to a pulse signal having a required voltage value. The pulse signal from the comparator is applied to a frequency-divider circuit for frequency-dividing the pulse signal into a signal having a given frequency, which is a clock signal.
This clock reproducing circuit, however, requires adjustment of the values of the coil and capacitor of the LC resonant circuit, requires adjustment for correct resonance, and requires a larger number of circuit components. In order for the resonant circuit to resonate, a pull-in time is required, which worsen response of the circuit.
An object of the present invention is to provide a clock reproducing circuit that requires no adjustment, requires fewer components, and has good response.